Note that if you start KDiff3 with the command line option --reverse then all layouting will be done right to left too. (This is a feature provided by Qt™.)
kdiff3 opens the GUI then fails to open the files at first, showing two dialogs. Then after I close the dialogs, kdiff3 manages to open the files correctly.
KDiff3 is a versatile file and directory comparison tool that merges up to three files, highlights differences with color-coded syntax, and resolves conflicts. Changelog · About Us · Screenshot · Guide
Via --config you can specify a different config file. When you often use KDiff3 with completely different setups this allows you to easily switch between them.
KDiff3 is a file and directory diff and merge tool which compares and merges two or three text input files or directories,shows the differences line by line ...
kdiff3 is a program that compares two or three input files, shows the differences line by line and character by character, provides an automatic merge-facility.